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Abstract

We show that phase objects may be computed accurately from a single color image in a brightfield microscope, with no hardware modification. Our technique uses the chromatic aberration that is inherent to every lens-based imaging system as a phase contrast mechanism. This leads to a simple and inexpensive way of achieving single-shot quantitative phase recovery by a modified Transport of Intensity Equation (TIE) solution, allowing real-time phase imaging in a traditional microscope.

Figures (7)

Design of a chromatic 4f system for differential defocus of colour channels. a) Chromatic defocus causes different colors to focus in different planes along the optical axis, b) quantification of chromatic defocus for three values of f2 given f1 = 200mm (at 532nm) with BK7 lens dispersion.

Nonlinearity error of a test phase object (inset) for varying values of wavelength and distance-dependent defocus. In the absence of noise, the error goes asymptotically to zero with decreasing defocus. Thus, the noise floor will determine the accuracy of the system.

Comparison of results from our technique with profilometer data from a commercial interferometer. (a) Height map from Zygo interferometer compared to (b) height map from our technique (µm). (c) Cross-section along one actuator of the DM array, showing the ‘influence function’ of the DM using both techniques.

Comparison of phase results from our technique with traditional TIE. (a) Phase from traditional TIE using two images (radians), (b) phase from our technique using a single color image (radians) and (c) the difference between the two results (radians).